Abstract: BACKGROUND: Matrine exerts therapeutic effects on pneumonia, sepsis, and hepatitis B because of its significant anti-inflammatory and anti-tumor properties. However, its role and mechanisms in macrophage-mediated inflammation post myocardial infarction remain poorly understood.
OBJECTIVE: To investigate the effects of matrine on inflammation and myocardial tissue repair following myocardial infarction, and to clarify its potential molecular mechanism.
METHODS: (1) In vivo experiment: 32 Sprague-Dawley rats were randomly divided into sham operation group, myocardial infarction group, low-dose matrine [200 mg/(kg·d)] group, and high-dose matrine [300 mg/(kg·d)) group, with 8 rats in each group. Myocardial infarction model was established in rats. Matrine was continuously gavaged for 3 days after surgery. On day 4, echocardiography and serum inflammatory cytokine levels were detected, and heart tissues were obtained for hematoxylin-eosin staining and Masson staining to evaluate myocardial injury severity. (2) In vitro experiment: Mouse bone marrow-derived macrophages were isolated and treated with 10 or 20 μmol/L matrine after lipopolysaccharide was given to establish an inflammatory model. The expression levels of M1/M2 macrophage polarization markers (inducible nitric oxide synthase, CD86, arginase-1, CD206) and their proportional changes were analyzed by western blot, RT-qPCR, and flow cytometry. Phosphorylated levels of Janus kinase 2, signal transducer and activator of transcription 3 were assessed by western blot. Additionally, H9C2 cells were subjected to hypoxic injury to evaluate the effect of matrine on cellular reactive oxygen species levels.
RESULTS AND CONCLUSION: (1) In vivo experiment: matrine intervention significantly improved cardiac function in myocardial infarction rats. Compared with the myocardial infarction group, both low- and high-dose matrine treatments significantly increased left ventricular ejection fraction and left ventricular fractional shortening in rats. The high-dose group demonstrated more pronounced improvements than the low-dose group. In addition, matrine significantly inhibited the increase of peripheral inflammatory factors (interleukin 1β and interleukin 6) after myocardial infarction. Histopathological analysis showed that matrine effectively reduces myocardial inflammatory cell infiltration, tissue edema and necrosis. (2) In vitro experiment: RT-qPCR and western blot results showed that matrine significantly downregulated the expression of M1 macrophage markers (inducible nitric oxide synthase and CD86), while upregulated the expression of M2 markers (arginase-1 and CD206). Flow cytometry indicated decreased proportion of CD86-positive cells, and significantly increased proportion of CD206-positive cells. In addition, matrine significantly reduced the intracellular reactive oxygen species levels. (3) Signaling pathway research: Western blot analysis revealed that matrine significantly inhibited the phosphorylation of Janus kinase 2 and signal transducer and activator of transcription 3, thereby blocking pro-inflammatory signaling pathways and promoting macrophage phenotype switching, ultimately achieving anti-inflammatory effects. These results indicate that matrine dose-dependently promotes macrophage polarization toward the M2 phenotype by inhibiting the Janus kinase 2 and signal transducer and activator of transcription 3 signaling pathway, thereby attenuating post-myocardial infarction inflammatory responses and exerting cardiomyocyte-protective effects.

Key words: matrine, macrophage polarization, myocardial infarction, inflammatory response, Janus kinase 2 (JAK2), signal transducer and activator of transcription 3 (STAT3)